In order-picking stores or systems as known from practice, the rack-serving unit is moving either fully- or semi-automatically into rack or rack aisles, wherein the storing boxes or compartments are of a depth of simple to multiple dimensions of the articles to be held in stock. The rack-serving unit loads articles into predetermined storing boxes and retrieves articles therefrom, for instance articles ordered for individual order-picking in order to deliver these articles to peripheral conveying units. The known rack-serving units widely correspond to conventional robots and just differ from these with regard to technical specifications such as degrees of freedom, working radius and space and kinematics. Handling articles is becoming more and more complicated when the packages or handling units by which the articles are made available are too many-faceted and too sensitive and no transport or loading facilities such as shelves, boxes, trays etc. are to be used. It is difficult or almost impossible to develop rack-serving units for handling more than e.g. 50 forms of packages and/or for being adaptable to the changes in design and shape of the packages. In such cases, a gripper changing system is usually used for robots with small working space. However, owing to the large working space and the bulk of the load pick-up device, this is hardly possible for rack-serving units. In practice, automatic order-picking warehouses without load pick-up device presently can only deal with packets, i.e. only packages with smooth, stable surfaces and a square shape can be managed. Furthermore, the coefficients of sliding and static frictions of the packages have to be low in order to enable the rack-serving unit to handle such packages by means of the load pick-up device in a technically comprehensible semi- or fully-automatic manner.
From experience, a rack-serving unit with the product labeling BEELAG of the Beewen Company and including a load pick-up device has been known, whose fork-like load transport gripper includes two parallel belt conveyors transversely spaced with regard to the telescoping direction and being telescopic relative to the load pick-up device towards one side of said load pick-up device until they are positioned below the opening of the bottom of the box, load the articles lying thereon at the lower side thereof and pull out these articles from the storing box and place them on stationary belt conveyors of the load pick-up device. As each of the article transport grippers can either be moved in or out at only one side of the load pick-up device, another article transport gripper that can be telescoped in the opposite direction is required for serving or operating storing boxes provided on the opposite side. The two belt conveyors of each of the article transport grippers are spaced apart from each other such that the loaded or grasped articles may assume a stable position thereon when being transported either into or out of the storing box. However, the space between the belt conveyors accounts for an extremely wide opening of the box bottom so that the box bottom is merely defined by narrow blades provided on both sides. That is why the articles can only be handled by means of loading equipment (paperboard, containers or trays, or the like), thus entailing undesired large additional efforts and diminishing the order-picking warehouse capacity.